Selected Financial Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) Segment segment	Mar. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Revenue	$ 687.6	$ 619.3
Number of Reportable Segments | Segment	3
Number of Corporate Units | segment	1
Unrealized Gain (Loss) on Securities		5.3
Gain (Loss) on Sale of Assets and Asset Impairment Charges	$ 1.8	(5.3)
Loss Contingency, Loss in Period	30.5
Reimbursement	(0.1)
Write off of Deferred Debt Issuance Cost	(0.5)
Currency remeasurement	4.9	0.3
Loan Related Fees	0.4	0.4
Loan Related Fees - Hedge Fees	0.2
EBITDA [Abstract]
Segments Adjusted EBITDA	289.1	267.2
EBITDA Adjustment - Corporate Expense	(25.8)	(28.3)
EBITDA Adjustment - Net Interest Expense	(35.8)	(43.5)
EBITDA Adjustment - Depreciation and Amortization	(90.3)	(93.5)
EBITDA Adjustment - Acquisition Related Revenue Adjustment	0.0	(4.2)
EBITDA Adjustment - Stockbased Compensation	(2.3)	(12.7)
EBITDA Adjustment - Mergers and Acquisition	(4.3)	(11.3)
EBITDA Adjustment - Accelerated Technology	(2.5)	0.0
EBITDA Adjustment - Other	(35.7)	(0.7)
Less: net income attributable to the noncontrolling interests	(4.1)	(2.4)
EBITDA Adjustment - Total	(192.5)	(191.7)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	96.6	75.5
Income (Loss) from Equity Method Investments	2.6	3.8
Acquisition-related Costs [Member]
Segment Reporting Information [Line Items]
Business Combination, Acquisition Related Costs	2.1	0.9
Fair Value, Inputs, Level 3 [Member]
Segment Reporting Information [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings	0.3	0.9
UNITED KINGDOM
Segment Reporting Information [Line Items]
Gain (Loss) on Sale of Assets and Asset Impairment Charges	(1.8)
U.S. Markets
Segment Reporting Information [Line Items]
Revenue	421.9	368.8
EBITDA [Abstract]
Segments Adjusted EBITDA	171.5	142.0
Income (Loss) from Equity Method Investments	0.6	0.6
U.S. Markets | Financial Services [Member]
Segment Reporting Information [Line Items]
Revenue	230.4	189.1
U.S. Markets | Emerging Verticals [Member]
Segment Reporting Information [Line Items]
Revenue	191.5	179.7
International
Segment Reporting Information [Line Items]
Revenue	157.7	146.0
EBITDA [Abstract]
Segments Adjusted EBITDA	60.2	65.0
Income (Loss) from Equity Method Investments	1.9	3.2
International | CANADA
Segment Reporting Information [Line Items]
Revenue	26.5	23.0
International | Latin America [Member]
Segment Reporting Information [Line Items]
Revenue	24.3	25.3
International | UNITED KINGDOM
Segment Reporting Information [Line Items]
Revenue	48.8	42.2
International | Africa [Member]
Segment Reporting Information [Line Items]
Revenue	14.3	15.0
International | INDIA
Segment Reporting Information [Line Items]
Revenue	30.8	27.7
International | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Revenue	13.0	12.8
Consumer Interactive
Segment Reporting Information [Line Items]
Revenue	126.7	123.4
EBITDA [Abstract]
Segments Adjusted EBITDA	57.4	60.2
Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue	706.3	638.2
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	(18.7)	(18.9)
Intersegment Eliminations [Member] | U.S. Markets
Segment Reporting Information [Line Items]
Revenue	(17.1)	(17.5)
Intersegment Eliminations [Member] | International
Segment Reporting Information [Line Items]
Revenue	(1.3)	(1.2)
Intersegment Eliminations [Member] | Consumer Interactive
Segment Reporting Information [Line Items]
Revenue	(0.4)	(0.2)
Callcredit [Member] | Acquisition-related Costs [Member]
Segment Reporting Information [Line Items]
Business Combination, Integration Related Costs	3.8	$ 4.2
Fraudulent Incident [Member]
Segment Reporting Information [Line Items]
Other General and Administrative Expense	$ 0.2